This invention generally relates to hand-held plastic containers for storing and dispensing particulate matter. More particularly, it relates to such containers with a cover having self-closing, spring-loaded flaps that stay in a substantially closed position even when they are unlatched.
Containers for retail products are almost always filled and packaged automatically. The containers are typically routed into narrow channels or troughs that guide the containers down filling, capping, labeling and packaging assembly lines through the factory,
In food and medical product manufacturing lines, the containers are most commonly guided by stainless steel rods. Channels made of stainless steel rods can be more easily cleaned using steam and chemical sprays. Regular cleaning after every shift or every day is commonly performed on food and pharmaceutical packaging lines. The rods that form the container-guiding channels are dried easily and do not trap food that can cause bacterial growth.
The channels typically operate using gravity. Occasionally a drive belt supplements these gravity channels while the containers are upright, resting on moving belts, restrained on either side by fences of stainless steel rods that prevent them from falling off the belts. In both arrangements, the containers are rather tightly constrained to prevent the assembly line from jamming. Side rails prevent them from moving side-to-side with significant free play.
One drawback to these processes is their ability to become jammed by containers that catch on the bottom or sidewalls of the channels. For this reason, the containers and tops are designed carefully to eliminate protrusions that might catch on the channels and jam. It only takes a small force, especially in a gravity-fed channel, for containers to stick. One method of reducing the possibility that the flaps will stick during processing is to design them with no protrusions or irregularities and a downward spring effect keeping them close.
U.S. Pat. No. 4,693,399 illustrates a successful cap design that limits jamming: it has a substantially flat top with flaps that do not protrude from the upper surface. The flaps extend to the outer edges of the cap, and together with the sidewalls, define a substantially smooth cylindrical outer surface with a diameter that is substantially the same as the diameter of the body of the container. Yet even this cap is not as good as it can be. The cap of the ""399 patent has flexible flaps that are attached to the body of the cap with living hinges formed integrally with the flaps and the body of the cap. As with many integral flap caps, the flaps of the ""399 cap are formed by injection molding when they are in a 90xc2x0 open position. Once the plastic has cooled to the extent it is solid, it then extracted from the mold and the flaps are closed. Since it is formed and cooled in an open position, there is a residual springiness in the hinge when it is closedxe2x80x94a tendency to self-open perhaps 30 or 45 degrees. As a result, if the latch is released during packaging the cap tends to spring open and stay open. Unfortunately, this often causes the container to become jammed in the channels.
One method of reducing this risk is described in U.S. Pat. No. 5,330,082 assigned to Weatherchem Plastics. The cap shown in the ""082 patent has a catch that reduces the risk that a flap will open. Instead of having a flange that grips the inside of the covered hole, such as is shown in the ""399 patent, the ""082 flap wraps around the outside of the hole and pulls inward. As the ""082 patent states, this arrangement causes the flap to hold even tighter to the cap as the cap is tightened to the bottle. When the cap is over tightened, the flap is holds ever more tightly to the body of the cap.
While this does reduce the chance that the flap will open and cause the container to be jammed in the assembly line, it suffers from the same drawbacks as the ""399 cap: once the flap is opened, it tends to spring to a half-open position. Since both the ""399 cap and the ""082 cap are integrally formed, they must be made in a flap-open position and later closed. If the flaps pop open for any reasons, they try to return to their as-molded positions. Once the latch or catch releases, they almost immediately spring open. While the ""082 patent reduces the possibility that the flaps will spring open, it does not reduce the possibility that flaps sprung open will jam the assembly line.
A person unskilled in the art may well wonder how one could continue a filling and packaging process knowing that a flap of a container was open. Wouldn""t the contents of the container spill out when the flap was unlatched, even if it did not open entirely? This may be true of many packaging processes, but not all. Many materials, especially food materials, have an heat induction liner inside the cap that is sealed to the top of the bottle. The cap serves to hold the inner liner in place. In these types of containers, the seal is pushed in using a lining machine. When the flaps open, the seal is still in place and the food material inside cannot escape even though the flap is unlatched. No food can escape or be contaminated merely due to an unlatched flap. As an example, consider the powdered Parmesan and Romano cheese containers for sale in any grocery store. When purchased at the store, all of these containers have an inner liner that must be peeled off in order to gain access to the contents. No food can come out even if the flaps are fully open.
It is the goal of this invention to provide a cap and a process for making that cap that reduce the possibility that its flaps, once unlatched, will spring open toward an as-molded position. It also a goal of this invention to provide a cap with a living hinge that is plastically deformed during cooling to make the flap self-closing. It is also a goal of this invention to provide a filling process for a cap with an internal liner that permits filling and packaging to continue without stopping the assembly line even when the flaps are unlatched.
In accordance with a third embodiment of the invention, a container is disclosed that includes a substantially cylindrical receptacle, comprising a circular sidewall, a bottom fixed to and enclosing the lower end of the circular sidewall, and an open upper end, the upper end having a circular opening substantially the same diameter as the outer diameter of the circular sidewall, the upper end having external threads; a circular sealing disc bonded to the top of the receptacle to substantially prevent the entry of water or air into the receptacle; a cap body screwed onto the receptacle and enclosing the circular opening, the cap body further comprising a cylindrical sidewall with internal threads configured to mate with the external threads of the receptacle, and a substantially flat top; a substantially flat flap having a central portion that is depressed with respect to a rim portion of the flap; and a living hinge integrally formed with the flap and the cap body, and hingeably coupling the flap to the cap body to permit the flap to open and close, the hinge having a sufficient displacement in a central portion thereof to retain the flap in a closed position when the flap is not latched in the closed position.
In accordance with a third embodiment of the invention, a container is disclosed that includes a substantially cylindrical receptacle, comprising a circular sidewall, a bottom fixed too and enclosing the lower end of the circular sidewall, and an open upper end, the upper end having a circular opening substantially the same diameter as the outer diameter of the circular sidewall, the upper end having external threads; a circular ceiling disc bonded to the top of the receptacle to substantially prevent the entry of water or air into the receptacle; a cap body screwed onto the receptacle and enclosing the circular opening, the cap body further comprising a cylindrical sidewall with internal threads configured to mate with the external threads of the receptacle, and a substantially flat top; a substantially flat flap having a central portion that is depressed with respect to a rim portion of the flap; and a living hinge intricately formed with the flap and the cap body, and hingeably coupling the flap to the cap body to permit the flap to open and close, the hinge having a sufficient displacement in a central portion thereof to retain the flap in a closed position when the flap is not latched in the closed position.